1. Field of the Invention
The present invention refers to a valve device comprising a valve having an outlet passage, a stationary surface, a support member provided at a distance from the stationary surface and rotatable about an axis, and a membrane provided between the stationary surface and the support member in such a manner that when the rotatable support member is in a first rotating position in relation to the stationary surface the membrane covers an orifice associated with the outlet passage and located at the stationary surface and when the support member is in a second rotating position said orifice is uncovered.
2. Description of the Prior Art
In many different fields magnet valves are used, for instance, as servo valves or control valves in different systems and arrangements working at high or low pressures, e.g. milking machines. Such magnet valves have the disadvantage that they are relatively heavy and large. Therefore, they require much space and may not be used on smaller arrangement components, especially not if these should be movable between different positions in a flexible and easy manner. Furthermore, such magnet valves are frequently energy requiring, partly due to the fact that the magnet requires continuous current supply in order to maintain at least one of the positions of the valve.
WO-A-8 201 924 discloses such a valve device initially defined and comprising a valve housing having an inlet passage and an outlet passage. The inner surface of the valve housing comprises an orifice associated with one of the passages and a rotatable support member is provided in the valve housing at a distance from the surface. Between the support member and the surface there is an elastic membrane provided in such a manner that when the rotatable support member is in a first rotating position in relation to the stationary surface the membrane covers the orifice and when the support member is in a second rotating position said orifice is uncovered. The rotatable support member comprises a longitudinal axis about which it is rotatable in relation to the surface and which is parallel to the surface. In most of the embodiments disclosed the membrane is formed by a closed band loop loosely, which is located between the surface and the support member and, which, due to the rotation of the support member, is rolling on the surface between a position over the orifice and a position beside the orifice. Consequently, the exact position of the membrane may be difficult to determine based on the rotating position of the support member. Moreover, this document discloses an embodiment in which the membrane is attached to a plane surface and to a displaceable pulling bar, the membrane being rolled over an outlet orifice provided at the plane surface by the displacement of the pulling bar from one end position to another.
EP-A-532 618 discloses a similar valve device initially defined and comprising a valve housing having an inlet passage and an outlet passage. In the valve housing, there are provided a stationary inner cylindrical envelope surface and a rotatable valve body at a distance from this surface. Between the inner cylindrical envelope surface and the valve body, there is a membrane provided in such a manner that when the valve body is in a first rotating position in relation to the cylindrical envelope surface the membrane covers an orifice associated with the outlet passage and located at the cylindrical envelope surface and that when the valve body is in a second rotating position said orifice is uncovered. Also according to this document, the longitudinal rotating axis of the valve body is parallel to the cylindrical envelope surface. In order to reduce the energy consumption, this document proposes the provision of a wing by means of which at least a part of the kinetic energy of the medium flowing through the valve may be recovered.
Due to the fact that the rotating axis of the valve body of these two known valve devices is parallel to the cylindrical envelope surface, the valve device becomes rather voluminous. Since the membrane has to have a certain length in order to be able to cover and uncover, respectively, completely the outlet orifice, the radius of the rotatable valve body has to exceed a determined value if the length of the rotating movement required should be limited to a quarter of a rotation, for instance. Consequently, the radius of the cylindrical envelope surface is given by the radius of the valve body plus said distance between the cylindrical envelope surface and the valve body, which in turn is determined by the thickness and the properties of the material used in the membrane.